Sound reproducing device



Patented Apr. 12, 1932 UNITED STATES PATENT OFFICE LEE DE FOREST, OF NEWYORK, N. Y., ASSIGNOB TO GENERAL TALKING PICTURES COR- PORATION, OF NEWYORK, N. Y., A CORPORATION OF DELAWARE SOUND REPRODUCING DEVICEApplication filed December 24, 1928.

This invention relates in general to sound reproducing devicesparticularly adapted for use in large auditoriums and the like inconnection with radio reception talking moi tion pictures and the like.

One of the objects of this invention is the provision of a new form ofsound reproducing .device of large size constructed to render it mobile.

A further object of this invention is the provision of a soundreproducing device of this type pivotally mounted on a carriage so thatit may be readily moved about and rotated on its pivots when desired.

A further object of this invention is the provision of a soundreproducing device in which a cone type of loud speaker is associatedwith an exponential horn, so as to load the cone speaker with a largeair column.

A still further object of this invention is the provision of a structureof the above type in combination with a plurality ofsound reproducingdevices adapted to reproduce the higher notes encountered in thereproduction of sounds.

A more general object of the invention is the provision of a soundreproducing device particularly adapted to reproduce faithfully all thefrequencies encountered in the reproduction of speech, music and thelike.

A further object of the invention is the provision of a structure ofthis type which is relatively simple to make and rugged and eflicient inoperation.

These and other objects as will appear from the following disclosure aresecured by means of this invention.

This invention resides substantially in the combination, constructionarrangement and relative location of parts, as will be disclosedhereinafter.

Referring to the drawings,- Figure 1 is a front elevational view of thedevice;

Figure 2 is a side elevational view; Figure 8 is a rear elevationalView; Figure 4 is a horizontal cross-sectional view taken on the line4-4 of Figure 1 Figure 5 is a vertical cross-sectional view taken on theline 5-5 of Figure 4:.

Serial No. 328,141.

In the use of sound reproducing devices in auditoriums and large roomsit is necessary to produce sufficient volume so that everyone in theroom may hear the sound reproduced distinctly without forcing thereproducing device to a point where it distorts the sound and introducesextraneous noises. It is also desirable to have a sound reproducingdevice which will reproduce all the frequencies normally encounteredfaithfully without discrimination in favor of any particular notes. Thedevice of this invention meets all these requirements in a simple anduseful manner. In addition the structure has been so gotten up that thereproducing device is rendered exceedingly mobile and is arranged sothat it may be materially reduced in height when desired and renderedaccessible for adjustment and repair.

As shown in the drawings, the device comprises a base member 1 supportedon pivoted rollers 2. Extending upwardly from the base member are twoconverging brackets 3 at the center of the platform laterally braced bymeans of the member 4. Extending vertically from the front edge of theplatform are the converging members 5. The memhere 3 and 5 have the samevertical height and are interconnected by a pivoted rod 7. Pivotallysupported on this rod is a large horn member 6 constructed of suitablematerial for the purpose in what is known as the exponential form. As iswell known in the exponential horn the cross-sectional area of the hornincreases from the small to the large end according to an exponentiallaw. The horn is of course, provided with the usual bell as indicated at8. Supported within this horn at the small end thereof is a cone type ofreproducer comprising the actuating unit 9 and the conical diaphragm 10.The horn 6 is separate from the casing within which the reproducer ismounted as shown in the drawings so that the horn can be moved on itspivot rod 7. The free edge of the cone is secured to the baflie board 10to block off the space below it. This board may or may not be secured tothe horn proper. As shown the diaphragm 10 has its free edge openingupwardly so as to be in fullcontact with the air column within the horn.Supported on the back of the horn are two actuating units 11 and 12connected to the metal trumpets 13 and 14 which extend through the bellof the large horn, so as to be adjacent the front thereof. The portionsof the trumpets and their actuating units are enclosed by means of thehinged cover 15. In using a device of this type an amplifier is employedhaving a number of channels, each adapted to pass most efliciently aparticular band of frequencies. The low frequency channels would beconnected to the cone reproducer at the base of the horn and the highfrequency channels would be connected to the trumpets.

By means of such an arrangement the large horn in combination with thecone loaded with a large air column would faithfully reproduce the lownotes and the trumpets would faithfully reproduce the high notes. Thesenotes issuing from the bell of the horn would blend into a compositewhole. By providing a movable support for the device, it is easy to moveit around especially in theatres in its use with talking motion picturesto permit moving it out of the way during actual acts on the stage.Furthermore by pivotally supporting the device on the rod 7, it ispossible to swing it horizontall to reduce its vertical height when thisis desirable. This also permits of easy access to the parts in adjustingthem. If desired the mouth opening of the bell may be covered with anysuitable fabric.

From the foregoing disclosure, it will be apparent that I have embodiedcertain principles in a physical construction which may be varied bythose skilled in the art without departing from these principles, and Ido not therefore desire to be limited to the disclosure given forpurposes of illustration, but rather to the scope of the appendedclaims.

What I seek to secure by United States Letters Patent is:

1. In a sound reproducing device as described the combination comprisinga support, rollers on said support to adapt it for easy movement, alarge horn pivotally attached to said support, means in the base of thehorn for reproducing sound, and a plurality of sound reproducing devicesattached to the horn, so that the sound reproduced thereby will blendwith the sound reproduced by the sound reproducing device in the base ofthe horn.

2. In a sound reproducing device of the type described the combinationwith an exponential horn, and a. sound reproducing device at the smallend of said horn whereby it is loaded by the air column within the horn,of a plurality of sound reproducing devices mounted on said horn andmetal horns projecting into said horn and connected to said soundreproducing devices.

3. In a sound reproducing device of the type described, the combinationcomprisin a cone loud speaker and a flared horn-shaped member withinwhich the cone loud speaker is placed so that the air column formed bythe member directly loads the cone of the cone loud speaker.

47. In a sound reproducing device of the type described, the combinationcomprising a horn having a mouth ortion, said horn having a relativelylong air column with re spect to its cross sectional area, and a conediaphragm mounted within said horn at the end opposite to the mouthportion thereof.

5. In a sound reproducing device of the type described, the combinationcomprising an exponential horn and a loud speaker having a conediaphragm mounted within said horn at the small end thereof so that thecone diaphragm is loaded by the air column formed by the exponentialhorn.

6. In a sound reproducing device of the type described, the combinationcomprising a horn, a sound reproducing device within said horn having adiaphragm, and a baflie within said horn to which said diaphragm isconnected.

7. In a sound reproducing device of the type described, the combinationwith a horn forming a relatively large air column, a loud speakermounted within said horn having a cone diaphragm, and a baffle extendingtransversely of the born to which said cone diaphragm is secured.

8. In a sound reproducing device of the type described, the combinationcomprising a horn having a mouth portion at one end and said horndiminishing in cross sectional area from the mouth portion to the otherend, a cone diaphragm mounted in the smaller end of said horn, a baflleextending across the horn near the small end thereof and connected tothe cone diaphragm so that the cone diaphragm is on the opposite side ofthe baffie with respect to the mouth of the born.

9. In a sound reproducing device of the type described, the combinationcomprising a horn forming an air column, a loud speaker having a conediaphragm mounted within said horn so that the cone diaphragm is loadedby the air column formed by the horn,.

and a baflle within said horn extending transversely thereof to whichthe cone diaphragm is attached, said bafiie being attached to said horn.

In testimony whereof I have hereunto set my hand on this 22nd day ofDecember A. D.,

LEE DE FOREST.

